Be electronic trans I mean the shifting is controlled by the TCU or ECU itself, the toyota elec trans has two solenoids to make up 4 speeds and one to lock the convertor.
The only time the trans downshifts to gear 1 is when the vehicle speed is nearing zero, the IDL switch in the throttle position sensor is triggered and the pressure control cable has released.
You are saying that you had a solenoid replaced earlier. It maybe that the same solenoid is now sticking.
the shift solenoids work like this example.
1 0 = gear 1
1 1 = gear 2
0 1 = gear 3
0 0 = gear 4
1 = on
0 = off
so if you sticking in second I can assume that solenoid S2 is sticking. btw how smooth does the trans shift? When you changed the solenoids did you use new or used parts?